1. Field of the Invention
The present invention relates to enhanced, flexible light weight energy absorbing materials and methods of making them. These materials have utility in the manufacture of personal protection equipment (PPE), such as soft armor, bullet, fragment, stab, spike and hypodermic needle protection systems.
2. Description of Related Art
U.S. Pat. No. 5,866,658 discloses thermoplastic compositions which are blends of highly-neutralized ionomers of copolymers of ethylene and high weight percentages of α,β.-ethylenically-unsaturated C3-C8 carboxylic acids dispersed in a continuous or co-continuous polyamide phase and further discloses a process for making such blends. The blends are particularly useful in applications such as molded parts where toughness, high gloss, abrasion/scratch resistance, UV resistance, high temperature properties and stiffness are desired.
U.S. Pat. No. 5,859,137 discloses thermoplastic ionomers based on ethylene/acid copolymer ionomers which contain both (meth)acrylic acid and certain dicarboxylic acid monomers. The polymers may be melt processed as readily as ethylene/(meth)acrylic acid dipolymer ionomers in contrast to ethylene/acid copolymer ionomers containing only dicarboxylic acid monomer derived in-chain acid units. Polymers with typical levels of (meth)acrylic acid and low levels of diacid provide ionomers comparable to existing ionomers but which have adhesive and polymer blend compatibilizing characteristics, while polymers with higher levels of diacid will exhibit properties which depend on in-chain diacid derived units.
PCT publication WO 01/037691 discloses a protective material comprising a plurality of separate flexible layers each layer comprising a plurality of high strength fibers capable of resisting penetration by a knife or sharp-pointed objects such as ice picks and hypodermic needles, and a support material, wherein at least part of the fibers are embedded within the support material to restrict relative movement of the fibers therein.
PCT publication WO 03/053676 discloses multiple threat penetration resistant articles. The articles include, in order, fabric layers, polymer impregnated fabric layers and woven fabric layers. The articles can additionally include tightly woven fabric layers which define the strike face of the article.
PCT publication WO 2011/156577 discloses a thermoplastic composition for manufacturing personal protection equipment for personal ballistic, stab and knife protection, wherein the thermoplastic composition comprises at least a first thermoplastic polymer that has a melting point different to the melting point of a second thermoplastic polymer.
PCT publication WO 2010/036406 discloses a method for producing fiber composites impregnated with a thermoplastic resin to be used as stab and ballistic composite structures.
PCT publication WO2008/105929 relates to adhesive compositions used in composite laminar structures to improve ballistic resistance, for example, which limits the penetration of a bullet from a gun. The composite laminar structures includes an aramid or olefin fiber layer, a eutectic impact absorbing adhesive resin or adhesive composition layer, and an ionomer layer. The aramid or olefin fiber layer is adhesively bonded with the eutectic impact absorbing adhesive resin or adhesive composition layer to the ionomer layer. In further embodiments, the composite laminar structure includes an olefin fiber layer, a eutectic amorphous acid functional polypropylene copolymer adhesive layer, and an ionomer layer. The olefin fiber layer is adhesively bonded with the eutectic amorphous acid functional polypropylene copolymer adhesive layer to the ionomer layer. The olefin fiber layer has no polarity within a matrix thereof and has no affinity for moisture.
PCT publication WO2006/069950 relates to a heat-shrinkable multilayered film comprising at least one carrier layer (a) based on at least one thermoplastic polymer, at least one gas barrier layer, and at least one sealing layer. The entire free surface of the carrier layer opposing the gas barrier layer is covered with an outer release layer having a plasticizing or melting temperature that is at least 30° C. higher than the sealing or melting temperature of the sealing layer.
U.S. Pat. No. 6,645,336 to Albertone describes a process for the preparation of a laminate, particularly a waterproof moisture vapor permeable laminate, comprising a substrate having on a surface thereof a thermoplastic polymer resin coating and further comprising a peelable release layer in contact with the surface of the thermoplastic polymer resin remote from the substrate, and optionally further comprising a tie layer between the substrate and the thermoplastic polymer resin, the process comprising the steps of forming or providing a substrate layer and providing on a surface thereof a thermoplastic polymer resin coating and a peelable release layer and optionally providing a tie layer between the substrate and the thermoplastic polymer resin coating, characterized in that the thermoplastic polymer resin has a viscosity less than about 3000 Pa·s measured according to the standard ISO11443.
PCT publication WO 2002/026463 discloses an efficient method of simultaneously molding multiple composite laminates comprising layering one or more layers of wet-laid, non-woven mats comprised of particulate thermoplastic polymer and a fiber reinforcement between one or more layers of a release film material and molding the combination to form multiple laminates.
There remains a need to further improve the flexibility of fabric-resin composites used in soft body armor without sacrificing protection against multiple threats such as bullet, knife, stab and needle attacks.